It's a fix! So claims Yulia Tymoshenko, the defeated candidate in yesterday's Ukrainian presidential elections. Even before a vote was cast, Tymoshenko had been warning her rival Viktor Yanukovych of "the kind of resistance he has never seen before" if he tried to rig the election. "If we are unable to guarantee the honest expression of the people's will and honest results, we will mobilise the people," she said. "I have no doubt about this."

Now that she has indeed lost we can prepare ourselves for days - even weeks - of protests as her supporters attempt to annul the result.

A sense of deja vu? Absolutely. We've been here a few times before.

In 2000, the self-styled 'democratic' opposition in Yugoslavia claimed that any result in the presidential election which did not show the incumbent Slobodan Milosevic defeated in round one would be a fix - and that they'd take to the streets. Which is what they did. In the so-called 'Bulldozer Revolution' which followed, parliament was set on fire and Milosevic lost power.

In 2009, the Iranian 'green' opposition declared that any result which showed the incumbent Mahmoud Ahmadinejad the winner in the country's presidential election would be fraudulent and that they'd take to the streets. Which is what they did.

So far Ahmadenijad's regime hasn't been toppled, but it's certainly been seriously weakened by the protests.

What the 'democratic' opposition in Yugoslavia, Iran and Ukraine have in common is that they were the favoured choices of the US. In the Ukraine, Yulia Tymoshenko may have modified her once fiercely anti-Russian position, but there's no doubting that the US would prefer one of the co-leaders of the US-backed 2004 'Orange Revolution' and a supporter of Nato membership to an opponent – i.e. Viktor Yanukovych - who is against joining Nato and wants his country to be neutral.

The opposition can make their claims about the election being fraudulent, before a vote is even cast, because they know that their cause will be championed by the US and its closest allies, including Britain. They also know that they will be sympathetically portrayed as 'democrats' in the mainstream western media - and that their rivals will be portrayed as 'cheats' and 'frauds'.

But how democratic is it if one side declares that, if the other side wins, it must be by cheating? The victory is already tarnished - even if no tangible evidence of electoral fraud ever emerges.

The opponents of the western-backed street protestors are faced with a dilemma: either stand back and lose power (as Milosevic did in 2000), or crack down violently on post-election protests, as the Iranian regime has done, and be condemned by "the international community".

The claims of the US-favoured side to have been cheated out of the election are allowed to go unquestioned by most mainstream western media. But we should not automatically presume that because the 'wrong side' from the west's perspective won, that there has been significant fraud.

After last year's Iranian presidential elections, former CIA field officer and Iran expert Robert Baer, a man who could hardly be accused of pro-Ahmadinejad bias, wrote a Time magazine article entitled 'Don't assume Ahmadinejad really lost'. In it, he challenged the dominant western narrative that there had been an illegitimate coup d'etat in Tehran.

Baer noted that "one of the only reliable, Western polls conducted in the run-up to the vote gave the election to Ahmadinejad by higher percentages than the 63 per cent he actually received". Baer also accused the western media of looking at Iran "through the narrow prism of Iran's liberal middle class — an intelligentsia that is addicted to the Internet and American music and is more ready to talk to the Western press".

In any case, the west's double standards when it comes to disputed election results are glaring. In the 2006 presidential elections in Mexico, official results showed that the neo-liberal, anti-leftist and pro-American Felipe Calderon had won by 0.58 per cent.

The left-wing 'Coalition for the Good of All' alleged voting irregularities in more than 30 per cent of polling stations and organised massive street protests. But the protesters' cause was not championed by Washington and the election controversy was barely mentioned in the mainstream western media. Why? Because the "right" side had won.

There was similar lack of interest about possible electoral irregularities when the fanatically pro-US 'Rose revolutionary' Mikheil Saakashvili won a scarcely credible 96 per cent of the vote in the 2004 presidential election in Georgia.

But when the leftist and independently minded Alexander Lukashenko polled 82.6 in the presidential elections in Belarus, it was a clear sign that the election had been fixed. The west championed the cause of the opposition candidate, Alexander Milinkevich, who, despite receiving just six per cent of the vote, called for the government's overthrow and Lukashenko's death.

If you're not the side that Uncle Sam favours then it seems you're just not allowed to win an election fairly and squarely. And, as Viktor Yanukovych may be about to find out, you should prepare for night after night of street protests, which will, courtesy of CNN and the BBC, be broadcast all over the world.